Search Publications
Tip of the Red Giant Branch Distances. I. Optimization of a Maximum Likelihood Algorithm
Dolphin, Andrew E.; Shaya, Edward J.; Tully, R. Brent +4 more
Accurate distances to galaxies can be determined from the luminosities of stars at the tip of the red giant branch (TRGB). We use a maximum likelihood algorithm to locate the TRGB in galaxy color-magnitude diagrams. The algorithm is optimized by introducing reliable photometric errors and a completeness characterization determined with artificial …
Coronal prominence structure and dynamics: A magnetic flux rope interpretation
Gibson, S. E.; Fan, Y.
The solar prominence is an example of a space physics phenomenon that can be modeled as a twisted magnetic flux tube or magnetic flux "rope." In such models the prominence is one observable part of a larger magnetic structure capable of storing magnetic energy to drive eruptions. We show how a flux rope model explains a range of observations of pr…
Direct x-ray constraints on sterile neutrino warm dark matter
Beacom, John F.; Watson, Casey R.; Yüksel, Hasan +1 more
Warm dark matter might more easily account for small scale clustering measurements than the heavier particles typically invoked in Λ cold dark matter (ΛCDM) cosmologies. In this paper, we consider a ΛWDM cosmology in which sterile neutrinos νs, with a mass ms of roughly 1 100 keV, are the dark matter. We use the diffuse x-ray…
The Extrasolar Planet ɛ Eridani b: Orbit and Mass
Kürster, Martin; Gatewood, George; Cochran, William D. +11 more
Hubble Space Telescope (HST) observations of the nearby (3.22 pc) K2 V star ɛ Eridani have been combined with ground-based astrometric and radial velocity data to determine the mass of its known companion. We model the astrometric and radial velocity measurements simultaneously to obtain the parallax, proper motion, perturbation period, perturbati…
Observations of Thick Disks in the Hubble Space Telescope Ultra Deep Field
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
The vertical profiles of chain and spiral galaxies in the Hubble Space Telescope Ultra Deep Field (UDF) are fit to sech2(z/z0) functions convolved with stellar profiles in order to measure the disk scale heights z0 in four passbands. The bulge regions of the spiral galaxies are avoided. Photometric redshifts give a…
Globular Clusters in Virgo Ellipticals: Unexpected Results for Giants and Dwarfs from Advanced Camera for Surveys Imaging
Brodie, Jean P.; Beasley, Michael A.; Strader, Jay +1 more
We have analyzed archival Hubble Space Telescope Advanced Camera for Surveys images in g and z of the globular cluster (GC) systems of 53 ellipticals in the Virgo Cluster, spanning massive galaxies to dwarf ellipticals (dEs). Several new results emerged. (1) In the giant ellipticals (gEs) M87 and NGC 4649, there is a correlation between luminosity…
Coronal Holes, Jets, and the Origin of 3He-rich Particle Events
Pick, M.; Mason, G. M.; Wang, Y. -M.
Using magnetograph measurements, coronal field extrapolations, and imaging observations, we investigate the solar origins of 25 3He-rich particle events from the period 1997-2003. In essentially every case we find that the source of the impulsive solar energetic particles (SEPs) lies next to a coronal hole containing Earth-directed open…
Minkowski's Object: A Starburst Triggered by a Radio Jet, Revisited
Stanford, S. A.; Morganti, Raffaella; Oosterloo, Tom +8 more
We present neutral hydrogen, ultraviolet, optical, and near-infrared imaging, and optical spectroscopy, of Minkowski's Object (MO), a star-forming peculiar galaxy near NGC 541. The observations strengthen evidence that star formation in MO was triggered by the radio jet from NGC 541. Key new results are the discovery of a 4.9×108 M…
XMM-Newton and INTEGRAL observations of new absorbed supergiant high-mass X-ray binaries
Parmar, A. N.; Walter, R.; Ubertini, P. +7 more
Context: .During the first year in operation, INTEGRAL, the European Space Agency's γ-ray observatory, has detected more than 28 new bright sources in the galactic plane which emit the bulk of their emission above 10 keV.
Aims: .To understand the nature of those sources we have obtained follow-up observations in the X-ray band with XMM-Newton.…
The Interaction of the Atmosphere of Enceladus with Saturn's Plasma
Gurnett, D. A.; Lewis, G. R.; Coates, A. J. +10 more
During the 14 July 2005 encounter of Cassini with Enceladus, the Cassini Plasma Spectrometer measured strong deflections in the corotating ion flow, commencing at least 27 Enceladus radii (27 × 252.1 kilometers) from Enceladus. The Cassini Radio and Plasma Wave Science instrument inferred little plasma density increase near Enceladus. These data a…